1. Field of Invention
This present invention relates to microscope objective lens systems and more particularly, to a plan-achromatic immersion type infinite microscope objective with numerical aperture 1.25 and a magnification of .times.100.
2. Description of the Related Art
For most known microscope objectives of this kind, i.e. immersion plan-achromat microscope objectives with numerical aperture of 1.25 and a magnification of .times.100, the chromatic, coma and spherical aberrations, astigmatic difference and curvature of field are not favorable.
Rosenberg U.S. Pat. No. 3,583,789 discloses at FIG. 4 a microscope objective which achieves a .times.100 magnification and which includes a plano-parallel plate CI. This objective lens is of the oil immersion type having a suitable liquid located between the cover glass surface and the plano-parallel plate CI. The rear surface of the plano-parallel plate CI is cemented to the plane surface of a hemispherical lens element CII. However, this microscope objective lens does not achieve sufficient aberration correction, and Rosenberg appears not to have recognized the problem with aberration correction in connection with such a plano-parallel plate.